High-quality GaN films grown on surface treated sapphire substrate

High-quality GaN films with low dislocation density have been successfully grown on the c-plane specially treated surface of the sapphire substrate. The vapour phase epitaxy starts from the regions with no etched pits where there are some micro-sidesteps to help to nucleate and then spreads laterally with increasing V/III ratio to form continuous GaN films. The full-widths at half-maximum of the x-ray diffraction curves for the GaN films grown on the treated surface of the sapphire substrate in the ( 0002) plane and the ( 10-12) plane are as low as 208.80 arcsec and 320.76 acrsec, respectively, and the etch-pit density of those etched in molten KOH is reduced to 5.5 x 10(5) cm(-2). The surface of the epilayer exhibits atomically smooth, whose root mean square roughness is found to be 0.2863 nm. The epilayer grown on the treated surface of the sapphire substrate exhibits excellent optical quality, in which the yellow luminescence is nearly invisible in the photoluminescence spectrum. Compared with the conventional epitaxial lateral overgrowth technique, the technology is much simpler and the crystallographic tilt can also be greatly decreased.